incorporate cell metadata element "scrolled" for conversion to html

[itcarroll]

Jupyter Lab has "Enable Scrolling For Outputs" as a right click option on cells. The option is embedded in a cell's metadata object under scrolled, and is popular for making notebooks much more readable when opened in Jupyter Lab.

The option does not appear to have any effect on jupyter nbconvert --to=html .... If paying attention to cell metadata is within scope for nbconvert, this would be a nice one to incorporate by applying overflow-y in CSS.